Where does “grugo” come from?

grugo (Welsh) comes from Welsh grug, from Middle Welsh gwrug, from Proto-Brythonic gwrʉg, from Proto-Celtic wroikos — heather.

Ancestry of “grugo”, step by step

StepLanguageWordMeaning
1Welshgrugheather
2Middle Welshgwrug—
3Proto-Brythonicgwrʉgheather
4Proto-Celticwroikosheather
Every word from Proto-Celtic wroikos →Every word from Proto-Brythonic gwrʉg →Every word from Middle Welsh gwrug →